As a flat display device, TFT-LCD (Thin Film Transistor Liquid Crystal Display) is applied in the field of high performance display increasingly because of its characteristics including small size, low power consumption, no irradiation, relatively low fabrication cost, etc.
As shown in FIG. 1a, a TFT-LCD comprises an array substrate 10 and a color filter substrate 11. A liquid crystal layer 12 is disposed between the array substrate 10 and the color filter substrate 11. Furthermore, a first polarizer 13 is disposed on an upper surface of the color filter substrate 11, and a second polarizer 15 is disposed between the array substrate 10 and a backlight module 14. In some embodiments, an optic axis of the first polarizer 13 is perpendicular to an optic axis of the second polarizer 15. If no electric field is applied to the liquid crystal layer 12, light emitted from the backlight module 14 will enter the liquid crystal layer 12 by passing through the second polarizer 15, and liquid crystal molecules will rotate the direction of the incident light, such that it will emit from the first polarizer 13. If an electric field is applied to the liquid crystal layer, the arrangement direction of liquid crystal molecules in the liquid crystal layer 12 will be changed, such that the incident light cannot penetrate it. As such, light intensity can be controlled accordingly, and a color image can be displayed by virtue of light filtration effects of the color filter substrate 11.
In prior art, said polarizer (the first polarizer 13 and the second polarizer 15) can be formed with a polyvinyl alcohol (PVA) thin film. One polarized component of natural light will transmit and another component will be absorbed by the polarizer. As such, it may cause a significant loss of light, and thus significantly decrease light utilization efficiency.
In order to solve above problems, in prior art, there provides a wire grid polarizer 20 formed of a metal material, as shown in FIG. 1b. When light enters the wire grid polarizer 20, with the oscillation effect of free electrons on a surface of the metal, light oscillating parallel to an electrical field vector component of the wire grid is almost all reflected, whereas almost all light oscillating perpendicular to the electrical field vector component of the wire grid transmits. Furthermore, the light reflected by the wire grid polarizer 20 can be reused, such that the utilization efficiency of light is improved effectively.
However, in prior art, during the process for manufacturing the above wire grid polarizer 20, a metal target material is required, which should be subjected to a evaporation magnetron sputtering process to form a metal thin film on a substrate, and thus there is a significant consumption of the target material. In addition, during the process for forming a wire grid pattern by a patterning process, a part of the metal thin film layer needs to be removed, resulting significant waste of the target material. Therefore, a prior art method has high cost because of the higher cost of a metal material.